Generally, an electrical connector used for a button battery, such as disclosed in Chinese patent issued publication No. CN101097998A, usually cannot detect whether the button battery is mounted to reach a predetermined position or not. If the button battery starts to use when the button battery is not mounted to reach the predetermined position, the button battery will easily looses or detach from the electrical connector due to vibration, and in turn will lead to the phenomenon of poor electrical contact or electrical interruption.